21156442 has 8 divisors (see below), whose sum is σ = 31756032. Its totient is φ = 10571100.

The previous prime is 21156419. The next prime is 21156463. The reversal of 21156442 is 24465112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1717 + ... + 6727.

It is an arithmetic number, because the mean of its divisors is an integer number (3969504).

Almost surely, 2^21156442 is an apocalyptic number.

21156442 is a deficient number, since it is larger than the sum of its proper divisors (10599590).

21156442 is a wasteful number, since it uses less digits than its factorization.

21156442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7124.

The product of its digits is 1920, while the sum is 25.

The square root of 21156442 is about 4599.6132446109. The cubic root of 21156442 is about 276.5758212082.

The spelling of 21156442 in words is "twenty-one million, one hundred fifty-six thousand, four hundred forty-two".